1. Field of the Invention
This invention relates to an electrophotographic photosensitive member and more particularly to an electrophotographic photosensitive member having a high electrostatic contrast and a distinguished durability stability.
2. Related Background Art
Recently, a large number of electrophotographic photosensitive members using organic compounds as photoconductors have been practically used, where photoconductive substances of relatively low molecular weight are dissolved or dispersed in a resin and applied to an electroconductive support to form a film thereon and are used in the form of devices in most cases.
Such a photoconductive layer has no sufficient adhesiveness to aluminum or vapor-deposited plastic films to be generally used as an electroconductive support in most cases. When a photoconductive layer is in a lamination form of a charge generation layer and a charge transport layer laid on the charge generation layer, the charge generation layer is generally a thin layer of not more than 1 .mu.m and thus is susceptible to influences of fine unevenness or irregularity of a support and it is difficult to form a uniform charge generation layer. Furthermore, the charge generation layer sometimes peels off due to poor adhesiveness to the support. Still furthermore, the charging characteristics of a photosensitive member is sometimes heavily deteriorated by charge injection from the support.
In order to improve the adhesiveness and film formability and prevent the charge injection, it has been practially used to provide an undercoating layer between a photoconductive layer, particularly a charge generation layer and an electroconductive support. Materials for the undercoating layer are required to be dissolved in a solvent and film-formable by application and, at the same time, not to be dissolved in such solvents as used in application of a charge generation layer and further a charge transport layer. Still furthermore, the materials, for undercoating layer must not deteriorate electrophotographic characteristics including a repetition durability. It has seen quite difficult to find materials for undercoating layer capable of satisfying all of these requirements. However, among others soluble nylons have been so far practically used owing to relatively distinguished characteristics (Japanese Patent Application Laid-Open No. 58-95351).
As one of the soluble nylons, N-methoxymethylated nylon 6, obtained by addition of a methoxymethyl group to nylon 6 is available. Electrophotographic photosensitive members comprising an undercoating layer containing the N-methyoxymethylated nylon 6, a charge generation layer and a charge transport layer succesively provided thereon have such a problem that the residual potential of electrophotographic photosensitive members is considerably increased by the physical porperties of a charge transport material.